Bacteria inhibited soluble oil



United States Patent 3,039,960 BACTERIA INHIBITED SOLUBLE OIL Edward'O." Bennett; Houston, Tex, assignortoTexaco Inc., .a corporation of Delaware No Drawing- Filed June 2,-1958,-'Ser. No. 738,981 3'Claims. (Cl. 252 -33.3)

This invention relates to a'soluble'oil inhibited against bacterial. action- More particularly, it relates to a bactericide containin'g solubleoil particularly useful in the form of an emulsionasametal working lubricant.

Soluble oils' generally'are composed of mineral oil or mixtures of mineral andvegetable oils, and an emulsifying agent to lower the interfacial tensionbetween the oil and large volumes of water whereby emulsions of the oil-inwater type may be easily formed; The emulsifying agents commonly used-include-soaps-of petroleum sulfonic acids, naphthenicacids, fatty acids, rosin and tall oil. Soluble oils usually containcoupling agents and small amounts of water to stabili'ze'the composition prior to emulsification. Variouslubricantadditives are also used to correct or improve'certain characteristics of the soluble oil orsoluble oil emulsion.

The oil-in-water emulsions are formed with water-tooil ratios ranging from 5:1 to-lOOzl. The more dilute emulsions, from 25 z-lto- 100:1 are preferred for cutting oils which are used as lubricants and coolants in high speed metal 'turning'operations.

The solubleoil itselfis shipped to the user, in a substantially sterile condition. However,- bacteria can be introduced in an emulsified soluble oil either through the water usedin the preparation thereof or through contamination bythe workers or from the air during use. The bacteria, if allowed to grow unchecked, will eventually cause breakdownof the emulsion and curtail the use for which it was intended.

In addition tothe aboveoccurrence, a serious odor problem is created by certain bacterial growth in the cutting fluid. Itisbelieved that initially the growth of certain aerobic bacteria takes place with a resulting slight breakdown of the emulsion. During shutdown periods of the'cutting'm'achinery, as on weekends and holidays, certain anaerobic sulfate-reducing bacteria grow quickly in the used cuttingfluid due-to inadequateaeration in the quiescent'systemand to the conditionsormaterial provided by the prior growth of aerobic bacteria inthe fluid. The presence of large amounts of sulfate-reducing bacteria causes severe odor problernsdue to the formation of sultides and the odor is particularly noticeable on Monday mornings afterweekend-shutdown periods. The growth of anaerobic bacteria also causes a quicker and more severe emulsion breakdown than is caused by aerobic bacteria necessitatingdraining and cleaning of the cutting fiuid system and the addition of new cutting fluid.

The problem of finding a satisfactory bacterial inhibitor for a soluble oil is made difiicult by a number of factors which must-beconsidered. These factors include toxicity, oil solubility, storage stability, emulsion degradation, additive compatibilityandgrowth inhibition of harmful bacteria for a sufficient period duringthe life of the oil.

In accordancewith' the present invention a soluble oil composition whichwill' meet'the above requirements contains abacteria-inhibitingamount of a"comp'ou1'1d having thefollowing general formula:

0 R-Hg-.-'-0ii-R wherein K isz'an'alkyl radical havingfrom 1 to 4 carbon atoms or an: alk'oxyalkyl radical wherein eachalkyl group has Efrom 1 to 4 carbon atoms :and R is' an alkyl group havingi from- 1 to-3rcarbon atoms. Preferred compounds of the above class are those wherein R is a methyl or 3,039,960 Patented June 19, 1962 2 ethyl group and R is a methyl group. A particularly preferred compound meetingthe aboveformulafis methyl mercuric acetate basis performance. Examples-of other useful compounds include:

Ethyl mercuric acetate Propyl mercuric acetate Butyl mercuric acetate M ethoxymethyl mercuric acetate Methoxyethyl mercuric acetate M ethoxypropyl mercuric acetate Ethoxymethyl mercuric acetate Ethoxyethyl mercuric acetate Ethoxybutyl mercuric acetate Propoxyethyl mercuric acetate Propoxybutyl mercuric acetate Butoxymethyl mercuric acetate Butoxyethyl mercuric acetate Methyl mercuric propionate Ethyl mercuric propionate' Methoxyethyl mercuric propionate Methyl mercuric butyrate Ethyl mercuric butyrate Methoxyethyl mercuric butyrate These compounds are effective in soluble oil emulsions in amounts ranging from 25 to 2500 parts per million. The preferred amount is about parts per million based on performance and cost. The amountsof these bactericides incorporated-in the soluble oil per se ranges from about 0.1 percent to about 6 percent by weight based on the oil. These amounts are sufficient to obtainthe proper concentration of bactericide whenthe emulsion is formed.

The soluble oil mainly comprises amineral lubricating oil and an emulsifying agent. The mineral oil is preferably a naphthene base distillate oil although mixed parafiin-naphthene base distillate oils are at times elfectively employed. Napht-hene base distillate fractions are desirable because of their better emulsification properties and stability. In general, refined base oil fractions having an SUS viscosity at 100 F. between 70 and 800 are used in the formulation of the soluble oils of this invention.

The emulsifying agents useful in the present invention are those known in the'art. Examples of these emulsifiers include oil soluble metal petroleum' sulfonates; alkali metal naphthenates, and resinates, salts of fatty and carboxylic acids, such as guanidine salts of high molecular weight fatty acids and alkylolamine salts of carboxylic acids containing at'least 10 carbon'atoms, alkali metal salts of tall oil, etc. These soaps or salts are'usually formed with sodium because of the lower costand availability, but potassium is also used. Mixtures of emulsifiers, for example a mixture of sodium naphthenate and sodium petroleum sulfonate, a mixture of sodium resinate, sodium naphthenate and sodium petroleum sulfonate, and a mixture of guanidine stearate and triethanolamine stearate have been found extremely useful.

The total emulsifier concentration is between 10 and 20 percent by weight of the total soluble oil composition with concentrations between 12 and 16 percent usually employed.

Minor amounts of coupling agents' are also advantageously employed in-the soluble oil composition to improve the texture and stability thereof. Those coupling agents useful in this invention include mono and polyhydroxy alcohols, ether-alcohols and phenols. Example s' of these compounds include ethyl, isopropyl,- n-propyL' isobutyl, n-butyl and n-amyl alcohols; ethylene glycol, dieth ylene glycol and propylene glycol; ethylene glycol monoethylether (Cellosolve), ethylene glycol monois'opropylether, ethylene glycol monobutylether, ethylene glycol mono-n-pentylether, ethylene glycol mono-n-hexylether,

diethylene glycol monoethylether (Carbitol), diethylene glycol monobutylether and cresol. The concentration of the coupling agents in the soluble oils is usually between 0.1 and 1.5 percent by Weight. A preferred coupling agent is ethylene glycol monobutylether at a concentration of about 0.6-1.0 percent by weight.

In preparing the soluble oil of this invention a small amount of water is preferably used to make the soluble oil fluid and to prevent oil separation, or stratification of the emulsion, upon mixing the soluble oil with much larger amounts of water. The water content, to stabilize the oil, usually falls between 1 and 4 weight percent. A water content of about 2 percent has been found to be particularly effective in the soluble oil composition.

Other useful lubricant additives, to improve certain characteristics of the soluble oil, are at times used in the composition. These include, for example, rust preventatives such as triethanolamine, extreme pressure and oiliness agents, and settling agents.

The bactericide of the invention is incorporated in the soluble oil before the oil is emulsified. It may also be incorporated in the emulsion at the time it is prepared and before any serious bacterial problem occurs, or it is added to the emulsion after a bacterial problem is evident thereby correcting said problem before serious degradation of the emulsion occurs.

In order to determine the value of compounds, known or expected to have bacteria destroying properties in water solutions, as bactericides in soluble oil emulsions, a screening test was used. This test consisted of preparing the cutting fluids or soluble oil emulsions and adding 100, 500, and 1000 p.p.m. of each bactericide to 20 ml. of the emulsion in test tubes. The tubes were then autoclaved at 15 pounds steam pressure for 15 minutes. After the tubes had cooled to atmospheric temperature, 0.5 ml. of a composite used cutting oil sample or inoculum was prepared by mixing the spoiled cutting oil samples of several users. The bacterial content of the inoculum was determined and in every case the tubes were inoculated with a standard known number of viable bacteria. Tubes of sterile uninhibited uninoculated emulsions and uninhibited inoculated emulsions were employed as controls. All tubes were placed on a shaking machine making 209 oscillations per minute. Immediately after inoculation of the emulsions and at 24 hour intervals for a period of 7 days, each tube was tested for the presence of viable bacteria by inoculating nutrient broth with a small standard volume of emulsion. were incubated for 48 hours and then examined for bacterial growth. Those bactericides which caused the inoculated emulsions to become sterile within the seven day test period were considered promising and were subjected to further testing. Of over 250 known bactericides tested in the above manner less than a third were considered promising for bacteria inhibition of soluble oils.

Effective materials found with the above test procedure were further tested in an Open System Test. The procedure consisted of placing 3.0 gms. of powdered iron and 3000 ml. of a 25 :1 soluble oil emulsion containing the experimental bactericide in a one gallon jar and inoculating with a known quantity of bacteria. The soluble oil consisted of a naphthene base distillate oil having an .SUS viscosity at 100 F. of about 72, 7.5 percent sodium resinate, 12.0 percent sodium petroleum sulfonate, 1.0 percent ethylene glycol monobutylether, 0.5 percent triethanolamine and 2.0 percent water. The system was then aerated for days and allowed to stand quiescent for 2 days each Week. Immediately after inoculation and twice a week thereafter duplicate standard plate counts were made. The inhibitors were considered effective as long as bacteria counts remained less than The following table shows the results of the Open System Test on the potential bactericides:

CAD

The broth tubes 4 Table I No. of Effective Days of Inhibition 1,000 p.p.m.

Sodium o-phenylphenate 3g o-Phenyl 'nn Pnnl ReSOrcin n1 Resorcinol dibenzoate Alkylamine o-phenyl pheno Mercuric naphthenate Zinc salt of alkylNpropylene-diamine-pentachloronhennl Pentachlorophon nl Tetradecylamine salt of ophenyl phenol Dichlorop ene Copper naphthenate, 8%. Azochloramide Mixture of 4 and 6 chloro-Z-phenyl phenol Methylene bis-phenol Tetrachlorophenol Dimethylaminomethyl phenol (0 and p mixture 2,4,6 lri(dimethylamino-methyl phenol) Beta-propiolactone- Diethyl acid pyrophosphate m-Oresol- 2-Methyl-1, t-naphthoq ne iLlPhenyl ethylamine Malouic acid 8 1,2-Dibromo-1,l-dichloroethane 0 Hydroxylamine, H01 sol Mixture of 2,8-diamino-10-methyl acr chloride and 2,8-diamino acridine Mixture of 2,8-diamino-l0-methyl acridinium chloride and 2,8-diamino acridine, HCl $01.. 2 Dichloro-m-xylennl Phenylmercuric acetate 26 92 Organic mercurial (Exact chemical composition not known) 1,2-Diehlorohexafluorocyclo-pentene-l Cyclohexyl chloride- 2 Amino-L4 naphthoquinone Propyl-p-hydroxyb cafe Butyl-p-hydroxyhen nate p-Chloro-m-xylenol 3 6 Lauryl isoquinolinium bromide Phenylmcrcuric monoethanolammonium acetatc Zinc salt of dimethyl dithiocarbamic acid 3,5-l )dibromo-2-phenyl mercurioiq benzoic aci Sodium salt of dibromohydroxy mercuric fluorescein (mercurochrome) Phenyl mercuric salicylate 1Hydroxy-2(1H)-pyridinethione (zinc salt) 1 Hy)droxy 2 (1H) pyridinethione (copper salt Morpholine silicofluoride. Rosin amine silicofluoride Methyl mercuric acetate test. However, this compound was not tested in the" Open System Test.

From the above data, it can easily be concluded that the mercuric compounds of the invention are exceptional for supprwsing aerobic bacterial growth in soluble oil emulsions.

Some of the compounds listed in the foregoing Table I were effective for more than 50 days in this test. However they were objectionable as either completely insoluble in soluble oil per se, decomposed in the soluble oil in storage, degraded soluble oil emulsion properties, or could only be incorporated in the soluble oil by utilizing a special technique which entailed adding the potential bactericide to ethylene glycol monobutylether, which is usually incorporated as a coupling agent, heating this solution to F. until the solution turned clear. The solution was then able to be added to the soluble oil.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A soluble oil which is normally subject to bacterial spoilage in metal working operations consisting essentially of a major proportion of mineral lubricating oil and 10-20 percent by weight of an oil-in-water emulsifying agent, containing a bacteria inhibiting amount of methyl mercuric acetate.

2. A soluble oil according to claim 1 wherein the said emulsifying agent is selected from the group consisting of oil-soluble alkali metal petroleum sulfonates, naphthenates, fatty acid soaps, resinates and tall oil salts and guanidine and alkylolamine salts of aliphatic carboxylic acids, and mixtures thereof.

3. A soluble oil emulsion which is normally subject to bacterial spoilage in metal working operations comprising from about 25 to 100 parts of water, about 1 part of an emulsifiable oil composition consisting essentially of a major proportion of a naphthene base distillate oil having an SUS viscosity range at 100 F. of from 70 to 800, from 12 to 16% by weight of a sodium salt of a compound selected from the group consisting of naph- References Cited in the file of this patent UNITED STATES PATENTS 1,993,776 Englemann et a1. Mar. 12, 1935 1,993,777 Englemann et al Mar. 12, 1935 2,044,959 Tisdale et a1. June 23, 1936 2,653,909 Frazier Sept. 29, 1953 2,668,146 Cafcas et al. Feb. 2, 1954 OTHER REFERENCES Pivnick et al.: Disinfection of Soluble Oil Emulsions, Journal of the American Society of Lubrication Engineers, March 1957 (pages 151-153 relied on).

Fundamentals of Microbiology, by Frolbisher, 5th edition, 1953, by W. B. Saunders Co., page 3 relied on. 

1. A SOLUBLE OIL WHICH IS NORMALLY SUBJECT TO BACTERIAL SPOILAGE IN METAL WORKING OPERATIONS CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF MINERAL LUBRICATING OIL AND 10-20 PERCENT BY WEIGHT OF AN OIL-IN-WATER EMULSIFYING AGENT, CONTAINING A BACTERIA INHIBITING AMOUNT OF METHYL MERCURIC ACETATE.
 2. A SOLUBLE OIL ACCORDING TO CLAIM 1 WHEREIN THE SAID EMULSIFYING AGEENT IS SELECTED FROM THE GROUP CONSISTING OF OIL-SOLUBLE ALKALI METAL PETROLEUM SULFONATES, NAPHTHENATES, FATTY ACID SOAPS, RESINATES AND TALL OIL SALTS AND GUANIDINE AND ALKYLOLAMINE SALTS OF ALIPHATIC CARBOXYLIC ACIDS, AN MIXTURE THEREOF. 